net/bnxt: fix ring teardown

net/bnxt: fix ring teardown

Check for valid bit while scanning for hwrm_done completion
during ring teardown. Not checking the valid bit could cause a
ring overflow when we ring the doorbell.

Fixes: 4fb6ab3f866d ("net/bnxt: check flush status during ring free")
Cc: stable@dpdk.org
Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>